Fixing up an AL-811H

[WB2WIK]

Any suggestions for an affordable "good enough" power meter that would handle 800 W PEP? I'd love one of N8LP's digital meters, but the cash isn't there for that right now.

Ken

This one works very well and isn't too expensive. I have two of them and use them all the time.

http://www.autekresearch.com/wm1.htm

[KC9TNH]

(Holy head-slap. Autek! duh) Thanks WB2WIK, their little RF1 tester looks pretty handy too.

[AG6K]

Ken,

That's all just nonsense.

The only reason that diode fails is the tubes flash over from gas, or from damage from melting the anodes down.

If you have repeated failures of that diode, it means you have a bad tube.

73 Tom

 Ken: If a tube turns out to be kaput I will pay the postage to have it sent here so I can do an autopsy and find out what happened, tnx.
• Rich, ag6k

[AG6K]

I agree that the AL-80B is a better amplifier than the AL-811H, especially when tube availability is factored in. However, I only have $3 invested in the AL-811H, so I'd like to get it working for my modest needs. The amp seems to be acting the way I'd expect after replacing the diode. The no-drive plate current is a little low (around 100 ma), but that seems to be in spec according to the manual.

My biggest issue is in my lack of experience with anything using vacuum tubes. The glory days of vacuum tubes took place before I was born. You might say this is more of a "learning by doing" project at this point than anything else. I need a better power meter than the Radio Shack meter I have to figure out how much power I'm putting into my load, and I'm planning to run a dedicated 20 amp 120 volt circuit to my shack location in the next few weeks to eliminate the room lighting dimming I'm seeing when the amp is keyed. I've been doing a lot of reading, and am currently using the tuning pulser method described on W8JI's site using the keyer in my radio sending dits at 60WPM.

Any suggestions for an affordable "good enough" power meter that would handle 800 W PEP? I'd love one of N8LP's digital meters, but the cash isn't there for that right now.

Ken

 Ken ----- I used to calibrate power meters in a cal. lab. IME they are less accurate than the speedometer on my 1973 Dodge Maxivan.
• Rich, ag6k

[WB2WIK]

 Ken ----- I used to calibrate power meters in a cal. lab. IME they are less accurate than the speedometer on my 1973 Dodge Maxivan.
• Rich, ag6k

All depends on the meter, though.

My 2001 Town & Country minivan's speedometer is very accurate, if I don't change the size of the wheels....

[KM1H]

With a caveat or three the AL-80B is a decent amp but it has a few idiosyncracies. Id buy a known good used one before new. The AL-80A is similar but has a weak transformer as do several budget amps.

Id like to see a 160-10M 2 x 572B amp running no more than 2000V which would be 1000W input at the rated 250ma Ip per tube. Figure on 600+ W out. The Chinese tubes still have some reliability problems but with less than usual HV and a carefully designed filament supply it should hold up OK.

Carl

[W8JI]

There is nothing wrong with the transformer in most AL80A's.

During one period in production Ameritron changed vendors from Schumaker to a vendor Heath used, and starting having the same problems Heath had with secondary to core or secondary to primary shorts.

About 50 to 100 units were affected by that out of over 2000-2300 units sold.

[N3JBH]

There is nothing wrong with the transformer in most AL80A's.

During one period in production Ameritron changed vendors from Schumaker to a vendor Heath used, and starting having the same problems Heath had with secondary to core or secondary to primary shorts.

About 50 to 100 units were affected by that out of over 2000-2300 units sold.

Tha sad thing is they all could have been saved with the correct parasict suppresor's

[W8JI]

Tha sad thing is they all could have been saved with the correct parasict suppresor's

Even flat tires can be avoided with nichrome lug nuts.

[AG6K]

All depends on the meter, though.

My 2001 Town & Country minivan's speedometer is very accurate, if I don't change the size of the wheels....

 Chrysler speedometers are very accurate but using plastic gears to drive the camshaft was undoubtedly daft.
• Rich, ag6k